A parallel hybrid vehicle which uses an engine and a motor in conjunction, and runs on the drive force of either or both of the engine and the motor, is disclosed by the following reference. "Automotive engineering" VOL.46, No.7, page 39-52, Tetsudo Nippon Co., June, 1997.
This parallel hybrid vehicle runs under the power of the motor in a low running load region, and starts the engine to increase drive force when the load increases.